A number of processes for producing compounds having a hydroperoxide group by oxidation of aromatic hydrocarbons substituted with an isopropyl group are known. There are, for example, a process for producing hydroquinone from p-diisopropylbenzene via p-diisopropylbenzene dihydroperoxide (see JP-A-48-72144, the term "JP-A" as used herein means an "unexamined published Japanese patent application"), a process for producing 2,6-dihydroxynaphthalene from 2,6-diisopropyl-naphthalene via 2,6-diisopropylnaphthalene dihydroperoxide (see JP-A-61-93156), and a process for producing 4,4'-dihydroxy-biphenyl from 4,4'-diisopropylbiphenyl via 4,4'-diisopropyl-biphenyl dihydroperoxide (see JP-A-64-75440).
In the working examples disclosed in the above-mentioned publications, the reaction is carried out in a reaction vessel made of Hastelloy B or C. Should the same reaction be performed in a reaction vessel, the part of which in contact with the reaction mixture is made of an iron-containing metal, which is cheaper than that made of Hastelloy and is generally employed in productive industry, the reaction is virtually suspended in its course, and the conversion of the secondary alkyl group does not increase any more.